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Voltage sensor for motor winding

Pragash A
Prodigy 140 points
Other Parts Discussed in Thread: MSP430F5132, INA240, OPA2374, DRV8303

Sir,

I have been into designing of sensorless control of switched reluctance motor where i need to sense the voltage across the winding. the system voltage is 48V, 3 A (max). Is there any products that will suit my need....

Thank you,

Pragash.A

  • 0
    Prodigy 5 points
    Hello Pragash,
    Winding voltage are typically sensed with a voltage divider and small RC filter that feed a uC or analog control.
    TIDA-00285 is an example.
    www.ti.com/.../TIDA-00285
    On the schematic page 5 in the upper left are the dividers used to interface to a MSP430F5132 MCU.

    The MCU connects on the schematic page 3 via a connector.

    Can you use a divider scheme to sense the voltages?
  • 0 in reply to Ed Walker
    Prodigy 140 points

    Hi,

    I just saw the schematics there as it is three phase BLDC, sensing the voltage with respect to ground is not a problem. But here it is switched reluctance motor, where the winding will be inline between the two switches of the asymmetric converter. So there may be switching disturbances caused due to the low side MOSFET switch right...

    But it may also work and i will try implementing it.

    Thank you,

    Pragash.A

  • 0 in reply to Pragash A
    TI__Genius 14825 points

    I believe the INA240 is a good choice to investigate for your application, if you have a 48V PWM signal and inline implementation of the current sense resistor.  There's an introductory app note about different implementations of current sensing for motors that details a bit about the INA240 and how it performs in an inline PWM application.  There is also a short "Tech Note" about inline current measurement that highlights the INA240 and a few other alternative devices.

    Let us know if that gets you started or if we've misunderstood your application needs and can provide better input.  We're here to help!

  • 0 in reply to Jason Bridgmon
    Prodigy 140 points
    Thank you very much for your reply. Actually i was asking about the voltage sensing IC. From the TIDA-00285 document i tried implementing the same circuit for my 48V system in simulation. I am getting saw-tooth waveform across the capacitor(although it is properly scaled within 3.3 V) the rise and fall times are very much higher which will tamper my reading with microcontroller. I tried reducing the value of capacitor from 0.1uF to 0.1 nF and then i got clearly scaled waveform. I am planning to proceed with this circuit and if there is anyother advice for the voltage sensing i am eager to hear about that.
  • 0 in reply to Pragash A
    TI__Genius 14825 points
    Are you referring to the DRV8303 integrated current sense amplifiers, or the OPA2374 op amp configured for current sensing? Or perhaps the ADCs on the C2000 microcontroller launchpad? I'm not sure I see any other voltage sensing on the board.